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The article by [Lee et al. (2004)][1] suggests that at least one “supereruption” from the Toba caldera, Sumatra, was associated with a climatic warming, rather than a cooling trend. The background to this is that [Rampino and Self (1992][2], [1993)][3] originally suggested that the supereruption

The 1815 eruption of Tambora is one of the largest explosive volcanic events of the past 10 000 yr. By a conservative estimate, 175 km3 of nepheline-normative trachyandesitic pyroclastic material (equivalent to about 50 km3 of dense rock) was erupted in 24 h. Major activity began with a brief plinian phase followed by pyroclastic flows; much of the ignimbrite that was produced shows evidence of deposition by turbulent flows. A 6×7-km caldera, about 1 km deep, formed at the end of the pyroclastic flow phase; caldera volume closely matches that of magma ejected. Plinian and co-ignimbrite ash fall >1 cm thick covered >500 000 km2 of the Java Sea and surrounding islands, accounting for more than two-thirds of the magma volume erupted. This distal tephra is known only from 1815 reports, indicating that some great eruptions, especially those from island volcanoes, may be virtually undetectable in the geologic record without supporting information, such as deep-sea core data. Land-based volume estimates may be insufficient to characterize eruption magnitude in many cases.

Wave-like bedforms of large amplitude and wavelength (6 m, 60 m) occur in an exposure at the base of the Fish Canyon Tuff, Colorado, an ignimbrite (ash-flow tuff) of great volume (> 3,000 km 3 ). The bedforms are located some 30–40 km from the center of the source caldera. They are interpreted to be deposits from a series of large pyroclastic surges, precursors to the main pyroclastic flows. The pyroclastic surge beds have bigger wave forms than those previously recognized. Such megawaves were perhaps produced by violent explosions related to major unroofing of a magma chamber. The depositional sequence of this great ignimbrite-forming event is similar to that of much smaller eruptions and implies a similar eruptive sequence.

Sinistral displacements across the North American–Caribbean plate boundary in northern Central America are distributed among major arcuate faults that have been active in Neogene time. South of the Jocotan and Motagua faults in Guatemala, extensional tectonics has accompanied rotation of the trailing edge of the Caribbean plate around these faults. Segmentation of the volcanic arc in northern Central America, hitherto attributed to transverse breaks in the subducting Cocos plate, may instead be a result of this block rotation. Accompanying changes along the arc are observed in seismicity, gravity anomaly patterns, volume and composition of volcanic products, and topography. Therefore, the complex volcano-tectonic geology south of the main boundary faults may be explained by interaction and rotation of crustal blocks in the overriding Caribbean plate above the magma production zone along the downgoing Cocos slab.

Several silicic units of the Trans-Pecos volcanic field have outcrop and thin-section scale features of lava flows but areal extents and aspect ratios of ignimbrites. These voluminous rocks (up to hundreds of cubic kilometres per unit) are quartz trachytes to low-silica rhyolites (68% to 72%SiO 2 ). Lava flow features include flow banding and folding, elongated vesicles, and autobreccias and vitrophyres at the base and top of units. Pyroclastic flow features include sheetlike geometry, lateral extents up to 70 km, aspect ratios as low as 1:700, and areal extents up to 3000 km 2 . A few of these units are clearly rheomorphic ignimbrites, but others show no unambiguous evidence of a primary pyroclastic origin. Although no adequate explanation currently exists for the origin of the latter, we evaluate two end-member hypotheses: (1) they are ignimbrites in which extreme rheomorphism has obliterated primary internal features, and (2) they are highly viscous lavas with unusually high heat retention or effusion rates that allowed them to spread over great areas. Either origin requires a rock type and eruptive mechanism not commonly recognized.

Many ignimbrite flow units show a reverse grading of large pumice clasts and a normal grading of large lithic clasts. Each ignimbrite flow unit has a basal layer finer grained than the body of the ignimbrite, with a ground surge deposit commonly underlying the ignimbrite, and a fine ash-fall deposit commonly overlying it. These two types of deposit, although not an integral part of the ignimbrite, are produced by the same eruptive act, and they and the ignimbrite constitute the several and varied products of a Pelean-phase eruption. Volcanic eruptions in which ignimbrite is generated show the following sequence of events so often that it may be regarded as the normal one: (1) a highly explosive, often Plinian, phase, producing a pumice-fall deposit; (2) a Pelean phase; and (3) an effusive phase, producing a lava flow. This sequence is believed to represent the tapping of progressively deeper levels in the magma chamber and the escape during the eruption of magma of progressively lower gas content.